Aziridines are versatile building blocks in organic synthesis due to their ability to undergo highly regio- and stereoselective ring-opening reactions to give diverse nitrogen containing compounds (Tanner et al. Angew. Chem. Int. Ed. Engl. 1994, 33, 599; Maligres et al. Tetrahedron Lett. 1997, 5253). Several efforts toward developing a direct aziridination of unfunctionalized olefins using transition metal catalysts have been made (Kwart et al. J. Am. Chem. Soc. 1967, 89, 1951; Mansuy et al. J. Chem. Soc., Chem. Comm. 1984, 1161; Evans et al. J. Org. Chem. 1991, 56, 6744; Vedejs et al. Tetrahedron Lett. 1992, 3261; Sodergren et al. Tetrahedron Lett. 1997, 6897).
In 1984, Mansuy reported a Fe(III)- and Mn(III)-porphyrin-catalyzed aziridination of unfunctionalized olefins with (N-(p-toluenesulfonyl)imino)phenyliodinane (PhI=NTs). Subsequently, Evans reported a copper-catalyzed aziridination of unfunctionalized olefins with PhI=NTs, and the asymmetric version of this reaction was later developed by the employment of chiral ligands (Lowenthal et al. Tetrahedron Lett. 1991, 7373; Li et al. J. Am. Chem. Soc. 1993, 115, 5326; Evans et al. J. Am. Chem. Soc. 1993, 115, 5328; Nishikori et al. Tetrahedron Lett. 1996, 9245; Osborn et al. Tetrahedron: Asymmetry 1997, 8, 1693).
Also, the direct aziridination of allylic alcohols has been reported using quinazolones as the nitrogen source in the presence of lead tetraacetate as a catalyst (Atkinson et al. J. Chem. Soc., Chem. Comm. 1988, 624). Although the reaction conditions for aziridination with PhI=NTs and quinazolones as the nitrene precursors are relatively mild and effective, much better methods for direct aziridination of olefins are needed before this transformation can be regarded as useful, even for laboratory-scale synthesis. The use of PhI=NTs is limited due to its complexity of preparation from (diacetyliodo)benzene and instability due to its high reactivity.
Our interest in the development of more efficient olefin oxidation processes has lead us to seek a general catalytic aziridination of olefins. What is needed, therefore, is an economically accessible method for the direct aziridination of olefins. Furthermore, what is needed is a stable and effective catalyst for the direct aziridination of olefins with a practical nitrogen source.